The present invention relates to curable bisimide resin compositions. The curable bisimide resin compositions of the present invention may be used for the production of fibre reinforced resins. For this application it is one possibility to prepare the resin composition in the form of a solution which is used to impregnate fibrous materials. It is advantageous to prepare the bisimide impregnating solutions with as large a bisimide content as possible. However bisimide compounds such as 4,4'-bismaleimidodiphenylmethane have limited solubility in the commonly used solvents and this limits the concentrations which can be employed. Another possibility for the impregnation of reinforcing fibres is to use molten resins. However, bismaleimides such as 4,4'-bismaleimidodiphenylmethane show a high tendency to crystallize and therefore do not provide stable melts at low temperatures.
It is one object of the present invention to provide solutions of curable bisimide resin compositions for use in the production of fibre reinforced resins in which as high a concentration as possible of 4,4'-bismaleimidodiphenylmethane is present. It is another object of this invention to provide curable bisimide resin compositions for use in the production of fibre reinforced materials in the form of a stable non-crystallizable melt in which as high a proportion as possible of 4,4'-bismaleimidodiphenylmethane is present.